Semiconductor device having the effect that the drop in the current gain is kept to the minimum, when the substrate density is amplified and that the variation in the collector current is improved

摘要

A semiconductor device includes a SiGe base bipolar transistor. The SiGe base bipolar transistor includes an emitter layer, a collector layer and a SiGe base layer formed of silicon containing germanium. A Ge concentration of the SiGe base layer is increased from 0% to 10% from a side of the emitter layer towards a side of the collector layer.